The incident occurred in village Garthwalia in Khalilabad area in which Aryan was killed and his parents and brother were seriously injured, they said.
This morning while Rajkumar was asleep on the terrace of his house with his family, he was allegedly attacked by Omkar and his aides with axe, Superintendent of Police (SP) Shailendra Kumar said.
While Aryan died on the spot, Rajkumar, his wife Pramila and their son Ankit sustained injuries in the attack and were rushed to a hospital, where their condition was stated to be serious, he said.
Police have arrested the main accused, Omkar, and his mother Shanti Devi.